Conventional traveling-wave tubes utilize a slow wave structure through which an electron beam passes. In the traveling-wave tube, electrons in the beam travel with velocities slightly greater than that of a radio frequency wave, and on the average are slowed down by the field of the wave. A loss of kinetic energy of the electrons appears as increased energy conveyed to the field of the wave. The traveling wave tube may be employed as an amplifier or an oscillator.
Staggered traveling-wave tube circuits in the prior art have an overlapping vanes with a small beam tunnel through the overlapping vanes. This type of prior art is illustrated in U.S. Pat. No. 6,747,412, teaching the use of a slow-wave structure of two intermeshing combs in combination with other components.
It had been settled wisdom that to have sufficient beam-microwave interaction strength to amplify a microwave signal, the circuit vanes, comb teeth, or simply parts must overlap to form a folded waveguide circuit. Having non-overlapping or intermeshed parts in a functional circuit was thought to be impossible.
A folded waveguide circuit also has strong symmetric field for the lowest mode. The microwave electron circuits in the frequency range below 100 gigahertz (GHz) have been manually fabricated by mechanical machining techniques. As the operation frequency of microwave amplifiers has increased, cutting-edge Micro-ElectroMechanical Systems (MEMS) techniques, such as lithography and etching, have become the preferred approaches to fabricate micro-circuits. However, despite many attempts and progress to three-dimensionally micro-fabricate folded waveguide traveling-wave-tube circuits, construction of the beam tunnel across the waveguides has always been problematic.
A key innovation of the present invention is a configuration that enables the elimination of interleaved, overlapping or intermeshing vanes.
In addition, other conventional traveling-wave-tube circuits such as the helix transmission line, folded waveguide, coupled-cavity, and conventional single- and double-vane-based circuits, and others, have technical limitations in high-frequency applications that result in lower performance levels than with the present invention.